As there seems to be some interest, I will give a bit more information.
I discovered Bitcoin in June 2011 while I was bored at work. First bubble, up to 30$ ! I bought the way up and the way down to 5$. Baby roller coaster. I came for the money, stayed for the tech and the possible money. And the drama.
Between 2011 and 2013 I decided to accumulate 100 bitcoins in total. I thought it was enough to be filthy rich if it was a success and not lose too much if it was a failure (3500$ or something).
Having spent not much on it, it was easier not to sell. I kept telling myself that it was worth a few thousands, not hundreds thousands. When it reached 9000$, I set selling points such as 1BTC at 10000, 1BTC at 12000, etc… I sold half of my bitcoins following this plan, in 2017. I continue to follow the plan. I remove the emotional factor as much as I can.
I am nevertheless reconsidering from time to time, because things change and I change. I am now wondering if I will not sell half of the stash in one go.
Alts: I got interested in many of them and bought quite a few. Always with bitcoins so it was like free money. My feathercoins, peercoins, namecoins are not worth much now 
See below for the ones I really like.
Security: having cryptos is a heavy work. Really. I had to learn a lot. I now have secured the cryptos in a way that should prevent hacking and personal threats. In particular I use multi-sig, one of them by a notary.
If you mean how much of my net worth would disappear shall BTC fail, around 35%.
My other cryptos do not account for much. I personally like ETH, I was part of the ICO and followed since then. If you have to pick one, pick this one. Also Monero: it has proper privacy and tries to be ASIC resistant. BCH: (I don’t want to start a war) that was the vision for Bitcoin in the early days, i.e. to be able to use the currency for transactions and not only as a store of value.